Browser extensions are small programs that can be used to add new features to a browser or modify the existing functionality. It is preferable for a browser extension developer to create extensions to work across all browsers, such as MICROSOFT EDGE, GOOGLE CHROME, APPLE SAFARI, and MOZILLA FIREFOX.
However, creating an extension that is compatible with different browsers can be very time consuming. Every browser has its own differences in terms of design and behavior. Therefore, the syntax for an extension might be different from browser to browser, which requires extension developers to insert code that workaround those differences for each of the different browsers. Currently, to reuse an existing extension on a different browser, extension developers must create logic in their extension code that checks for the different browser's host, e.g. checking for user agent string.